Growing out of control, cancer cells produce malignant tumors Cancer is a general term for many diseases in many animals and plants involving uncontrolled cell division with the resultant tumor metastasizing. (Spreading/growing) A malignant tumor consists of cancerous cells. These tumors metastasize. Benign tumors do not metastasize. Types: Carcinomas- Internal & External coverings Ex: Skin and intestine Sarcomas- Support tissue Ex: Muscle and bone Leukemia and Lymphomas: blood tissue Ex: bone marrow, spleen, lymph
8.9 Growth factors signal the cell cycle control system –The cell cycle control system regulates the events of the cell cycle –If a growth factor is not released at three major checkpoints, the cell cycle will stop G 1 of interphase G 2 of interphase M phase –How a growth factor might affect the cell cycle control system Cell has receptor protein in plasma membrane Binding of growth factor to receptor triggers a signal transduction pathway –Molecules induce changes in other molecules Signal finally overrides brakes on the cell cycle control system
LE 8-9a G 1 checkpoint G0G0 G1G1 G2G2 G 2 checkpoint M checkpoint M S Control system
LE 8-9b G 1 checkpoint G1G1 G2G2 M S Control system Growth factor Plasma membrane Relay proteins Signal transduction pathway Receptor protein
–Cancer cells divide excessively –Cancer cells spread from a malignant tumor –Metastasis is the spread of cancer Tumor Glandular tissue A tumor grows from a single cancer cell. Lymph vessels Cancer cells invade neighboring tissue. Metastasis Cancer cells spread through lymph and blood vessels to other parts of the body Figure 8.9
Genes and Cancer A gene encodes information for the production of a specific protein molecule. It is made up of a nucleotide sequence on a section of chromosomal DNA. When the gene sequence is altered (mutated), it may produce an abnormal protein. Cell division is regulated by a network of proteins. If one or more of these proteins become abnormal, a cell may continue to divide when it should stop. The genes implicated in cancer development are classified into three types:nucleotide Oncogenes - which stimulate cell division excessively. Tumor Suppressor Genes - which inhibit cell division and/or cause apoptosis (cell suicide). Mutations in tumor suppressor genes would promote cell division or allow genetically damaged cell to grow out of control. (p53) DNA Repair Genes - which correct the mutations of a gene. Mutations in DNA repair genes can lead to a failure in repair, which would allow other mutated genes to remain abnormal.
What can cause it? Causes of Gene Mutations –Inherited –Acquired after birth –Virus –Free radicals –Radiation or chemicals (Carcinogens) Asbestos*
Age And Risk -Because a number of mutations usually must occur for cancer to arise, the chances of developing cancer increase as a person gets older since more time has been available for mutations to accumulate. -For example, a 75-year-old person is a hundred times more likely to develop colon cancer than a 25-year-old, because the older person has a longer exposure time to factors that may promote gene mutations linked to cancer.
Stages Starting the Tumor Grading Process Illustration by National Cancer Institute, Pat Kenny (artist) A pathologist looks at the tumor cells and checks for three microscopic features: degree of tumor tubule formation (percentage of cancer composed of tubular structures) tumor mitotic activity (rate of cell division) nuclear grade (cell size and uniformity) Each feature is scored on a scale of 1 - 3. Cell Feature Scoring Feature Score 1: Slow cell growth rate Feature Score 2: Intermediate cell growth rate Feature Score 3: Fast cell growth rate
HW Research one type of cancer to discuss Cervical Colon Breast Pancreatic Lymphoma Brain Thyroid Testicular Ovarian Skin Who is affected? What are the risk factors? What environmental factors can cause it? Survival rate? Write down 10 facts that you are going to share with the class.